University of Wisconsin - Extension

MADISON, Wis.-- Unsafe nitrate levels showed up on thirteen percent of 115 well water samples in a screening conducted by University of Wisconsin-Extension at the 2002 Farm Progress Days in Richland County. Nitrate-nitrogen greater than 10 milligrams per liter (mg/L) of water is considered unsafe.

The high nitrate samples came from ten different Wisconsin counties. Overall, people from thirty counties brought water to be checked at this year's Farm Progress Days. The average nitrate value found was five mg/L; the highest was 30 mg/L, three times the safe limit. Fifty percent of the samples had low nitrate levels of two mg/L or less.

"Some of the people who brought water to be tested were unaware that their nitrate levels were high," said Chris Mechenich, UW-Extension groundwater educator. "Nitrate in drinking water can't be tasted or smelled. In fact, some people with high nitrate water tell us their water tastes very good," she said.

High levels of nitrate in drinking water can cause "blue baby" disease in infants less than six months of age, according to Mechenich. Women who are trying to conceive or who are pregnant should not drink water with high levels of nitrate because some researchers believe it increases the risk of birth defects and miscarriages.

People without infants in their homes should also be concerned about elevated nitrate levels. Recent studies in Nebraska and Iowa have suggested links between high nitrate drinking water and cancer. High nitrate levels do not occur naturally in Wisconsin groundwater, so they indicate that some human activity is contaminating the water, Mechenich said.

Lawn and crop fertilizers, manure storage and application, compost piles, on-site wastewater treatment systems and feedlots can contribute to high nitrate levels in groundwater.

"In Wisconsin, about 70,000 to 80,000 private wells may contain unsafe levels of nitrate," Mechenich adds.

Although information is incomplete about the long-term effects of high nitrate levels on adults, identifying nitrate in water should motivate homeowners to identify the source, and other possible groundwater contaminants from that source. In some cases, homeowners will need to repair or replace their well to solve nitrate problems. In other cases, a water treatment device can bring nitrate down to acceptable levels. Mechenich urges homeowners to choose a device certified by the Wisconsin Department of Commerce to remove nitrate or any other contaminant identified in the water. "However, what we'd really like to accomplish is to implement land management strategies that will prevent nitrate problems in the first place", she said.

The Wisconsin Department of Natural Resources (DNR) recently produced a brochure called "Nitrate in Drinking Water" (PUB-DG-001 2002) which is available from regional DNR offices. For more information about water testing, contact Christine Mechenich, UW-Extension groundwater educator, at 715-346-4276 or email to cmecheni@uwsp.edu.